/Engine/Source/Runtime/RHICore/Public/RHIPoolAllocator.h
Stats.
void UpdateMemoryStats ( uint32 & IOMemoryAllocated, uint32 & IOMemoryUsed, uint32 & IOMemoryFree, uint32 & IOMemoryEndFree, uint32 & IOAlignmentWaste, uint32 & IOAllocatedPageCount, uint32 & IOFullPageCount )